"There are two ways," Trump said, "quotas and tariffs. Maybe I'll do both."

The Commerce Department has been conducting a review of both steel and aluminum imports under a rarely used 1962 statute designed to protect industries deemed vital to national security. Secretary Wilbur Ross told reporters in April that imports now account for more than a quarter of the U.S. steel market, while domestic steel mills are operating at just 71 percent of capacity.

The Alliance for American Manufacturing, which represents steelmakers and the steelworkers union, supports new restrictions on imports. "If we don't step up now, America's entire aluminum and steel industries could disappear," the alliance warns on its website, "and we'll have to rely on Russia and China for our national defense needs."

Restricting steel imports through tariffs or quotas would be controversial, though. It would potentially raise prices for steel consumers and could spark retaliation from major trading partners.

Although the administration blames China for most of the glut on the global steel market, allies such as Canada, Mexico and South Korea would likely be hard-hit by any import restrictions. Those countries could respond with limits of their own on U.S. exports.

This week, more than a dozen former White House economists signed a letter, urging the president not to take action against steel imports.

"The diplomatic costs might be worth it if the tariffs generated economic benefits. But they would not," the economists wrote. "Additional steel tariffs would actually damage the U.S. economy. Tariffs would raise costs for manufacturers, reduce employment in manufacturing, and increase prices for consumers."

Trump's comments in support of import limits were originally made to reporters "off the record," but the White House later agreed to make them public.